Conventionally, vehicles comprise reinforcement elements destined to protect the vehicle occupants in case of an impact, in particular a side impact, a front impact or a roof crush during a rollover accident, by limiting intrusions of any kind in the vehicle passenger compartment.
The reinforcement elements comprise, on each side of the vehicle, a body side structure forming a door frame, which is conventionally made of steel, and an underbody reinforcement element forming with a floor panel the vehicle underbody structure.
Reducing the overall weight of the vehicle is very desirable in order to reduce the energy consumption, so as to meet the future environmental requirements. It is thus desirable to reduce the thickness of the parts forming the vehicle, in particular the reinforcement elements, including the underbody reinforcement element.
However, simply reducing the thickness of the reinforcement elements generally leads to a degraded protection of the vehicle occupants against intrusions.
Steels having better mechanical properties such as yield strength or tensile strength may be used. Indeed, such steels provide an enhanced protection that lower grade steels for a given thickness. However, such steels generally have a lower formability.